394 PRINCIPLES OF CHEMISTRY 



the skin they break, and the corrosive formic acid enters into the 

 body); it is obtained during the action of oxidising agents on many 

 organic substances ; it is formed from oxalic acid, and under many 

 conditions splits up into carbonic oxide and water. In the formation 

 of formic acid from carbonic oxide we observe an example of the 

 synthesis of organic compounds, such as are now very numerous, and 

 are treated of in detail in organic chemistry. 



Formic acid, H(CHO 2 ), carbonic acid, HO(CHO 2 ), and oxalic acid 

 (CHO 2 ) 2 , are the simple organic or carboxylic acids, R(CHO 2 ) cor- 

 responding with HH and HOH. Proceeding from carbonic oxide, CO, 

 the formation of carboxylic acids is clearly seen from the fact that CO is 

 capable of combining with X 2 , that is, forming COX 2 . If, for instance, 

 one X is an aqueous residue, OH (hydroxyl), and the other X hydrogen, 

 then the simplest organic acid formic acid, H(COOH) is obtained. 

 As all hydrocarbons (Chapter VIII.) correspond with the simplest, 

 OH 4 , so all organic acids may be considered to proceed from formic 

 acid. 



In a similar way it is easy to explain the relation to other com- 

 pounds of carbon of those compounds which contain nitrogen. By way 

 of an example we will examine one class of such nitrogenous com- 

 pounds. There are ammonium salts, R(CNH 4 O 2 ) corresponding with 

 every carboxylic acid, R(CH0 2 ), which salts contain the elements of 

 water ; this, with the assistance of substances taking up the water, may 

 be separated with formation of a special class of nitrogenous organic, 

 or, as they are termed, cyanogen compounds, RCN, 32 because the group 

 or monovalent residue, or radicle, ON, is called cyanogen. From this the 

 connection of the most varied organic compounds is apparent, and it is 

 not only expressed in relation to their composition but by a multitude 

 of reactions. It is most important to turn our attention to the two 

 following circumstances : (1) We have already noticed the various 

 mutual transformations of the simplest organic acids, clearly explained 

 by the existence of carboxyl in their composition. In a similar way, in 

 many reactions, the various cyanogen compounds undergo mutual 

 transformation, especially hydrocyanic acid, H(CN), corresponding 

 with formic acid, H(CHO 2 ) ; cyanic acid, OH(CN), corresponding to 

 carbonic acid, OH(CHO 2 ) ; and cyanogen, (CN) 2 , corresponding with 

 oxalic acid, (CHO 2 ) 2 . The mutual transitions of cyanogen compounds 

 into one another were known much earlier than the doctrine of 

 carboxylic acids, and therefore Gay-Lussac acknowledged cyanogen, 



52 The connection of the immense series of cyanogen compounds with the rest of the 

 hydrocarbons by means of carboxyl was enunciated by me, about the year 1860, at the 

 first Annual Meeting of the Russian Naturalists. 



